This invention relates to a method of and apparatus for wrapping articles, and more particularly to a method of and apparatus for wrapping units such as reams of paper each in a wrapper constituted by a sheet of wrapping material such as paper or other suitable wrapping material. While reference herein for simplicity sake often is made to "reams", it is to be understood that the method and apparatus is operable for wrapping other units and that such reference does not limit the nature or scope hereof. It will be understood that a ream generally comprises a stack of five hundred sheets of paper, the sheets being 81/2" by 11" or 81/2" by 14" sheets, for example. Such reams are presently produced in vast quantities by means of an apparatus called a "sheeter", which cuts paper into sheets of the desired size (e.g., 81/2" by 11") and stacks up the sheets in reams of five hundred sheets.
The invention is generally in the same field as the methods and apparatus disclosed in U.S. Pat. No. 4,029,194 issued June 14, 1977, entitled Automatic Indexing and Transferring Apparatus, U.S. Pat. No. 4,073,375 issued Feb. 14, 1978, entitled Method of and Apparatus for Feeding Randomly Received Items, U.S. Pat. No. 4,193,491 issued Mar. 18, 1980, entitled Apparatus for Feeding Stacks of Sheets, Such as Reams of Paper, U.S. Pat. No. 3,458,026 issued July 29, 1969, entitled Article Spacer, U.S. Pat. No. 4,203,694 issued May 20, 1980, entitled Squaring Reams of Paper for Wrapping, U.S. Pat. No. 3,533,496 issued Oct. 13, 1970, entitled Method for Guiding while Longitudinally Conveying a Ream of Single Sheets of Paper, U.S. Pat. No. 3,861,120 issued Jan. 21, 1975 and U.S. Pat. No. 4,279,116 issued July 21, 1981, each entitled Wrapping Apparatus, U.S. Pat. No. 3,213,591 issued Oct. 26, 1965, entitled Packaging and Wrapping Machine, U.S. Pat. No. 4,011,155 issued Mar. 8, 1977, entitled Wrapped Package Inspection and Rejection Apparatus, and in the assignee's printed literature for its Model 66 wrapping apparatus (designed to operate at speeds between 20 and 41 reams per minute) and its Model 35 and 36 wrapping apparatus (designed to operate at speeds of up to 60 and up to 80 reams per minute, respectively). The disclosure of the assignee's literature as well as the disclosure of the cited U.S. patents is hereby expressly incorporated herein by reference.
Wrapping such reams of paper and especially wrapping them at relatively high production rates presents special problems. For one thing, it is difficult to maintain the integrity of the reams (i.e., maintaining the reams with all the sheets in register).
Also, problems are encountered because the reams are delivered to the wrapping apparatus with slight spacing irregularities between successive reams (in other words, the reams are randomly received, i.e., they are not exactly equally spaced from one another), and the rate at which the reams are delivered is not necessarily a fixed ratio relative to the speed at which the wrapping apparatus is operated (i.e., the sheeter, the ream delivery system and the wrapping apparatus may not share a common drive). The spacing variations between the reams and the differences between the delivery rate of the reams and cycling rate of the apparatus causes the reams to be delivered periodically in and out of phase with the cycle of the wrapping apparatus. This can result in jamming of the wrapping apparatus.
Problems are further encountered in accurately operating the web positioning, and wrapper sheet transferring portions of the wrapping apparatus which relate to supply of wrapper blanks for wrapping around the reams. These aspects of the wrapping operation are particularly important because the wrapping sheet is often imprinted. Unless these aspects are properly carried out, the web may be cut through the imprint or the wrapper sheet may be wrapped around the ream with the imprint improperly positioned on the ream. Prior art methods and apparatus for accomplishing web positioning and wrapper sheet transfer have utilized electronic controls (e.g., PC boards) for controlling the drives for the web positioning and wrapper sheet transferring mechanisms. Such electronic controls have been able to effect positioning of the web and wrapper sheets, but with ramped acceleration and deceleration of the web and wrapper sheets in a sort of glitch and hunt motion. The time constraints under which the web must be paid out, positioned and cut and under which the cut wrapping sheet must be subsequently transferred into position for draping over the ream require speeds of operation that can thus involve jerky starts and stops of the apparatus using such prior art methods and apparatus. Damage to the web and wrapper sheet and undesirable excessive wear of the wrapping apparatus components can result. Moreover, such prior art solutions are expensive.
Still further problems are encountered in operating the cutting mechanism. Prior art reciprocating guillotine cutting blade mechanisms create excessive noise and prior art rotary cutting mechanisms disposed above the plane of the web are difficult to adjust and to replace and they deleteriously interfere with the ability to position the subsequent wrapper sheet transfer mechanism (in the form of a vacuum belt to the underside of which the wrapper sheet is held by suction) in a manner so as to support the cut wrapper sheet against curling along its cut edge.
Finally, problems are encountered in handling of the reams during outfeed (which commences while the reams are in the process of being wrapped by the wrapping means), so as to insure that the reams are not damaged. High speed motion must be imparted to each ream as it is being acted upon by the wrapping means so as to effect its removal from the wrapping in an extremely expeditious manner to permit wrapping of the succeeding web. And yet, such high speed motion must be imparted to the stationary ream without damaging the ream or knocking the ream out of alignment. A greater variation in the speeds and a more gradual acceleration of the overhead discharge conveyor which effects removal or outfeed of each ream being acted upon by the wrapping means than has been possible with the prior art is required.
The aforementioned problems become particularly acute when the wrapping apparatus is operated at speeds in excess of 100 reams per minute. The prior methods and apparatus have worked acceptably at lower speeds of 60-80 reams per minute, but they have proved unsatisfactory and unreliable at higher operating speeds, i.e., at speeds in excess of 100 reams per minute. They either cannot operated at such speeds or cannot sustain such speeds, i.e., they have a very short service life at such speeds.